SRA Annual report 2021-22: Natural Flood Management (NFM) capital grant schemes
Natural flood management schemes begun or completed in 2021-22, funded or part-funded by Somerset Rivers Authority.
Mendip
In the SRA’s Enhanced Programme of works for 2021-22, part of the funding allocated to Hills to Levels was earmarked for NFM activities in Mendip. This was to enable Mendip District Council’s flood risk consultant to follow up on SRA-funded work done previously to analyse Mendip sub-catchments’ flooding problems, assess where things could most usefully be done that were not being done by others, and fix those gaps by developing ideas and encouraging people and organisations to act together. FWAG SW has been helping matters to progress, as with these two schemes in the Frome area in 2021-22.
Marston Park
A floodplain restoration scheme is being developed on part of the Marston Park estate near Frome, between Tuckmarsh Lane and Thickthorn Wood. Its main aims are to reduce downstream flood risks by slowing the flow of water, increase biodiversity and improve water quality.
Activities so far have included water level monitoring, an initial ecological survey by FWAG SW, a site walkover with an archaeologist from South West Heritage Trust and a topographical survey. Because Marston Park and Garden are Grade II Listed, and there is evidence within part of the site of a medieval shrunken settlement, only small-scale marsh and floodplain restoration works are being proposed.
This scheme is being led for the SRA by Mendip District Council’s flood risk consultant, following on from some initial work done by FWAG SW as part of the Somerset Frome Project initiated by the Somerset Frome Partnership.
It is hoped to carry out works in autumn 2022.
Witham Friary
A scheme to restore parts of the floodplain along Hermitage Stream at Holt Farm, Witham Friary, about halfway between Frome and Bruton. Hermitage Stream is a tributary of the River Frome. Works in autumn 2021 comprised:
- Lowering sections of the riverbank to let more water out on to the floodplain
- Creating leaky woody dams in the stream to help divert water out on to the floodplain
- Creating shallow scrapes to hold more water on the floodplain
- Using timber to roughen-up the floodplain and slow the flow of water
In late October 2021 – before the whole scheme was completed – monitoring after very heavy rain showed water being held back. The purpose of slowing the flow downstream is to reduce flood risks in Witham Friary and down towards Frome and the A362 at Wallbridge. Other benefits include better water quality, because of a reduction in the movement of sediments, and a wider, more varied corridor of wetland habitat for wildlife.
This scheme was jointly funded by Mendip District Council and Somerset Rivers Authority, as part of both the Somerset Frome Project and Hills to Levels. It was designed by Hydro-Morph Ltd and FWAG SW, with groundworks done by local contractors.
Somerset West and Taunton
Lower Lovelynch, near Milverton, Hillfarrance Brook, a scheme designed to reduce flooding and the amount of soil deposited on a troublesome corner on the B3187 between Wellington and Milverton. Too much water from an uncontained spring was flowing down onto the road.
Works consisted of four main elements:
- Digging a ditch to contain and divert water into an existing culvert to take water into an existing drainage pipe.
- Cutting grips to re-direct water onto grassland to slow its flow, allow for infiltration into the ground and for sediment to settle.
- Extending an existing grassland area and installing a silt trap.
- Installing raised banks to intercept and slow run-off, and stabilising those banks with hedge planting.
Lower Vexford, Yeaw Farm, Doniford Stream tributary, 330 metres of hedgerow have been planted along the contours of quite a steeply sloping field, to help slow the flow of water and reduce flood risks downstream. One 20-metre section was planted in triple-row formation to provide a thicker barrier to a stream that rises after heavy rain. This whole scheme was also designed to help improve water quality and create new habitats for wildlife.
Luxborough, Chargot estate, upper Washford catchment. Two schemes were combined here to manage arable field run-off and water from a spring, and slow their flow downstream through three main interlinked measures. In order of descent down the hillside, and in simple terms: 1) quite a large pond was created and connected to a new field drain which flows down into 2) an extended and restored silt trap which drains into 3) another large new pond which drains down into a swale.
The SRA paid 21.6% of the cost of these two schemes, which were designed as part of the Hills to Levels Multiple Benefits Project led by the Environment Agency and FWAG SW. The Multiple Benefits Project is otherwise funded through the Environment Agency’s Water Environment Improvement programme. The Project’s purpose is to demonstrate that multiple benefits can be delivered by working with natural processes and natural flood management techniques across small catchments such as the upper Washford. Here on the Chargot estate, for example, the lower pond was designed to have a base level of water for the benefit of wildlife. The landowner is thinking of paying for further refinements such as a manually controlled sluice structure.
The schemes’ main elements can be seen in this video, which includes interviews with Angelique McBride of FWAG SW and landowner Caleb Sutton, from 2 minutes 37 seconds (2:37”) to 3:49”: https://youtu.be/HuIivbT7a1Y
Roadwater, in a wet field by The Old Mineral Line coming into Roadwater, below Road Wood, a bunded scrape has been created to hold more water for longer before it reaches the Washford River. Materials excavated during the making of the scrape were used to build up the bund. The landowner paid for the scrape to be fitted with pond liner up to a certain level, so that it can hold some water all-year round, but also take excess floodwater when need be.
West Bagborough, Crossways Farm, Back Stream catchment. An existing field corner pond has been de-silted and enlarged, and its outlet re-fashioned, so the pond can now store more water, in a more controlled way, during periods of heavy rain.
Associated works in this small but sophisticated scheme included:
- creating a hedgebank uphill from the pond to intercept and slow surface water run-off
- creating a ditch to capture more field run-off and drain into the pond
- coppicing the south-west hedgebank along the pond to let in more light and reduce leaf litter
Between 2017 and 2021, the SRA has funded several other schemes in and around the parish of West Bagborough to help reduce flood risks.
South Somerset
Stoney Stoke, Lush’s Farm, 1125 trees, 450 shrubs and 892 metres of hedgerow have been planted across a sloping valley side, down which water flows into the River Pitt. Slowing the flow of this runoff will help to reduce flood risks downstream, and – by trapping sediment and reducing erosion – to improve water quality.
As the new trees, shrubs and hedgerow adjoin a recently created strip of woodland, they also extend a wildlife corridor for species including bats, birds, small mammals and invertebrates.
The SRA gave a grant for just under 68% of the costs of this scheme. Other funding came via the Environment Agency’s Brue Catchment Priority Project.